The adverse effects of a surge can cause premature or even catastrophic failures for most turbines and compressors. Rotating stall, which may be an indicator for incipient surge and sometimes causing premature failures by itself, can be identifiable from the sub-synchronous band spectrum obtained from a variety of types of signals.
Existing techniques detect rotating stall by directly comparing the frequency spectrum in a sub-synchronous band with preset thresholds obtained from the baseline spectrum. They utilize the fact that the stall incurs increased energy on certain frequency components that are fractions of the compressor speed, but often overlook the difficulties and the uncertainties involved in establishing a baseline for detection. As the frequency response and noise characteristics will vary significantly with respect to operational conditions, the existing techniques based on direct comparison may not provide reliable results.